/Engine/Source/Runtime/Analytics/AnalyticsET/Public/AnalyticsProviderETEventCache.h
Sets an array of attributes that will automatically be appended to any event that is sent. Logical effect is like adding them to all events before calling RecordEvent. Practically, it is implemented much more efficiently from a storage and allocation perspective.
void SetDefaultAttributes ( [TArray](API\Runtime\Core\Containers\TArray)< [FAnalyticsEventAttribute](API\Runtime\Analytics\FAnalyticsEventAttribute) > && DefaultAttributes )